I enjoy building test environments to help cement the concepts I read about.
In this case it’;s the changes to the source and destination MAC addresses of a frame at layer 2 while it passes through each hop on the way to the final destination. To watch this process I setup wireshark between each hop.
The topology was very simple, 2 hosts and 2 routers.
![Topology]({{ “/assets/images/2015/08/Topology.png” | absolute_url }})